LONDON — Britain and France are stepping up their cooperation in outer space, but in Europe they still move in very different orbits.

At a meeting on Friday designed to bridge differences between the two neighbors, Prime Minister David Cameron of Britain and President François Hollande of France agreed to invest in joint space technology, but then openly clashed over the future of the European Union.

Mr. Cameron’s ambition to revise the union’s rule book and renegotiate Britain’s terms of membership, before holding a referendum in 2017 on whether his country should stay in the 28-country bloc, was dealt a blow by the French president.

A change in European Union treaties, Mr. Hollande made clear, is “not a priority.” France wants a better-run union, he said at a televised news conference, but “if there are going to be amendments to the text, we don’t feel that for the time being they are urgent.”

Standing next to the French president at an air base in Oxfordshire, about 65 miles northwest of London, Mr. Cameron disagreed politely. “Europe needs to change,” he said. “We want to see that renegotiation.”

“There will be further treaty changes coming,” he insisted, adding that he wanted Britain to vote in 2017 “to be part of a reformed union.”

France and Britain have long been on opposing ends of the European Union, with Paris lobbying for deeper political integration and London preferring a larger but looser cooperation among European nations based chiefly on economic ties.

Under pressure from the anti-union United Kingdom Independence Party, which is gaining ground with voters, Mr. Cameron has vowed to loosen British links with the union, which has its headquarters in Brussels. He would have greater leverage to get what he wants in Europe if there were a treaty change giving all leaders veto power.

But like many politicians in France, who were stunned nine years ago when a French referendum on a painstakingly negotiated European Constitution failed, Mr. Hollande appears reluctant to embark on another big negotiation. He is not alone on the Continent. Germany, the union’s biggest nation, has cooled on the idea of significant treaty change, too.

Friday’s meeting, after which the two leaders lunched in a country pub, was the first Anglo-French summit meeting attended by Mr. Hollande. It came at a time of some turmoil for the French president, who languishes in the opinion polls and split from his partner, Valérie Trierweiler, following reports that he had an affair with another woman.

Asked by a British reporter if the president’s private life had made his country an “international joke,” Mr. Hollande declined to comment.

Both leaders did their best to highlight areas of common interest. The Brize Norton air base where they held talks is a “symbol of solidarity” between the two nations, Mr. Hollande said. From there 70 years ago, British planes flew missions in preparation for the D-Day landings in Normandy. More recently, planes took off from Brize Norton to refuel French aircraft involved in operations in Mali.

Britain and France are the two biggest military powers in the European Union, and agreements announced included an investment of nearly $200 million in developing armed drones and unmanned underwater vehicles able to find and neutralize seabed mines.

“We have agreed on an exciting new collaboration on space,” added Mr. Cameron, “that will create new economic opportunities for both our industries with a 15 million-pound investment paving the way for joint work on earth observation, telecommunications and space research.”

On economic policy, familiar differences surfaced. Mr. Cameron sidestepped the question of whether he agreed with a Conservative colleague in his cabinet, Grant Shapps, who said recently that the French economy had been “run into the sand.” Growth is rebounding more strongly in Britain, where Mr. Cameron’s Conservative-led coalition has been busy trimming public spending, than in France, where the Socialist Mr. Hollande lowered the retirement age soon after taking office.

“Both of us are facing situations where we have to take difficult economic decisions,” Mr. Cameron said diplomatically, welcoming more recent proposals by Mr. Hollande to reduce French labor costs.

“Of course we are not going to agree about everything,” he said. “François is a French Socialist and I am a British Conservative.”

A version of this article appears in print on , on Page A9 of the New York edition with the headline: France and Britain Agree on Outer Space, but Find No Common Ground on Europe. Order Reprints | Today’s Paper | Subscribe